The concept of Goal Orientations (GOs), which was initially developed in the area of educational psychology, is becoming more and more popular in organisational psychology. Although research on GOs has come a long way since the 1970s there are still a number of conceptual and operational issues which have yet to be addressed. These include issues with the definition, dimensionality, stability and specificity of GOs. It is considered essential to address these concerns because they greatly influence the reliability, validity and accuracy of GO research. Consequently, one aim of this study was to examine the dimensionality, stability and specificity of GOs. It is believed that once enough evidence regarding these issues is gathered this could be used to develop a comprehensive definition of GOs. This study aims to contribute towards gathering such evidence. GOs have been examined both in terms of profiles as well as in terms of individual GO scales (non-profile perspective) in the past. This study uses both perspectives in order to attempt to provide as much information as possible regarding the issues being investigated. Another aim of this study was to investigate the relationships between GOs and performance, mental effort and self-efficacy. Further knowledge of these relationships is considered to be of benefit to organisations. So as to achieve these aims a longitudinal study, consisting of a survey and an experimental study, was carried out. The survey sample consisted of 641 participants whilst the experimental sample was made up of 73 participants. The participants were mainly Loughborough University students. However, there were also a number of employed and retired individuals participating in the study. Quantitative analysis was deemed to be the most appropriate method of analysis to achieve the aims of this study. Data analyses were carried out using SPSS and Latent Gold software packages. The results point towards GOs not being as general and stable as initially assumed. There is a strong possibility of GOs being domain-specific. Consistent with a number of past studies, the approach GOs were found to be more strongly related to self-efficacy, mental effort and performance on tasks than the avoidance GOs. Moreover, the relationships between GOs and these variables seem to be moderated by task characteristics. The profile analyses results revealed that a number of GO profiles obtained in this study were very similar to those obtained in other studies. A closer look at these common GO profiles indicated that some profiles were consistently more strongly related to self-efficacy, mental effort and performance than others. This study provides a foundation for future research studies to build on in order to better understand the nature of GOs and their relationships with self-efficacy, mental effort and performance.